MIAMI (AP) — The makeup industry is trying to convince women that looking good on the outside starts from within — but it’s unclear whether the products they’re trying to hawk are safe and effective.

Big-name beauty companies and retailers including Sephora and Urban Outfitters are rolling out pills and drinkable liquids loaded with exotic herbs, vitamins, seeds, berries and substances such as collagen. The products promise to do things such as firm up skin and improve its natural glow.

The trend is picking up steam. Although a small portion of the $16 billion beauty products market, sales of beauty supplements targeting the face have grown from less than $1 million in 2013 to over $4 million in 2015, according to market research firm the NPD Group.

But unlike the instant glam provided by a swipe of blush or lipstick, pills and other so-called “nutraceuticals” add a layer of questions about safety and effectiveness as some consumers may see ingesting something in the name of looking lovely a lot differently than simply rubbing something into the skin. And similar efforts have tanked in the past: Industry titans such as Oil of Olay peddled vitamins promising glowing skin and hair more than a decade ago to no avail.

Today, companies are being buoyed by celebrities who swear by these ingestible beauty products. In January, actress Gwyneth Paltrow shared the recipe of a daily shake on her online magazine’s website goop — an almond milk-based concoction that includes a product from Moon Juice’s line, with ingredients that are said to create a glowing complexion and healthy hair. Actress Jennifer Aniston also has said she puts collagen peptides in her morning shake.

And there’s a movement by everyday people to incorporate natural products into their lives for everything from the foods they eat to dish soap and mascara they use. An entire generation of consumers has evolved from merely reading food labels to scrutinizing chemicals in everything.

“The theme across all consumer categories is more natural ingredients for all the products they’re purchasing,” said Sarah Jindal, a senior beauty analyst for Mintel. “That’s going to continue to become more and more important to the consumer.”